l1-2:csc210 2014-2015 ©dr. basheer m. nasef lecture #1 by dr. basheer m. nasef

L1-2:CSC210 2014-2015 © Dr. Basheer M. Nasef

Welcome toObject Oriented

With JAVALecture #1

ByDr. Basheer M. Nasef

L1-2:CSC210 2014-2015 © Dr. Basheer M. Nasef 2

Agenda

Introduction to Java ProgrammingExamples

L1-2:CSC210 2014-2015 © Dr. Basheer M. Nasef 3

Learning Strategies

A programming course is quite different from other courses.

In a programming course, you learn from examples, from practice, and from mistakes.

You need to devote a lot of time to writing programs, testing them, and fixing errors.


JDK & JRE ?

JRE (Java Runtime) is needed for running Java programs.

JDK (Java Development Kit), which includes JRE plus the development tools (such as compiler and debugger), is need for writing as well as running Java programs.

To write Java Programs, you should install JDK, which includes JRE.

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JDK EditionsJava Standard Edition (J2SE)

J2SE can be used to develop client-side standalone applications or applets.

Java Enterprise Edition (J2EE)J2EE can be used to develop server-side

applications such as Java servlets and Java ServerPages.

Java Micro Edition (J2ME). J2ME can be used to develop applications for

mobile devices such as cell phones. This Course (CSC210) uses J2SE to introduce

Java programming.

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Popular Java IDEs (Integrated development environment)

NetBeans Open Source by Sun Eclipse Open Source by IBM Borland JBuilder 2007 (Based on Eclipse)JCreator.

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Java Program

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Java programs consist of pieces called classes.

Classes include pieces called methods that perform tasks and return information when they complete them.

Programmers can create each piece they need to form Java programs. However, most Java programmers take advantage of the rich collections of existing classes in the Java class libraries, which are also known as the Java APIs (Application Programming Interfaces).


Java Program

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Thus, there are really two aspects to learning the Java "world."

The first is the Java language itself, so that you can program your own classes.

The second is the classes in the extensive Java class libraries. Throughout this course, we discuss many library classes.


Creating, Compiling, and Executing a Java Program

//This program prints Welcome to Java! public class Welcome { public static void main(String[] args) { System.out.println("Welcome to Java!"); }}

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Creating and Editing Using NotePad

To use NotePad, type notepad

Welcome.java from the DOS prompt.

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Creating, Compiling, and Running Programs

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Trace a Program Execution

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Enter main method



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Execute statement



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print a message to the console


Anatomy of a Java ProgramCommentsPackageReserved wordsModifiersStatementsBlocksClassesMethodsThe main method

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Comments

I. Line comment: A line comment is preceded by two slashes (//) in a line.

II. Paragraph comment: A paragraph comment is enclosed between /* and */ in one or multiple lines.

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javadoc comment: javadoc comments begin with /** and end with */. They are used for documenting classes, data, and methods. They can be extracted into an HTML file using JDK's javadoc command.

Three types of comments in Java.


Package

The second line in the program (package

chapter1;) specifies a package name, chapter1,

for the class Welcome. Forte compiles the source

code in Welcome.java, generates Welcome.class,

and stores Welcome.class in the chapter1 folder.

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Reserved WordsReserved words or keywords are words that have a specific meaning to the compiler and cannot be used for other purposes in the program.

For example, when the compiler sees the word class, it understands that the word after class is the name for the class. Other reserved words in above program are public, static, and void. Their use will be introduced later.

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ModifiersJava uses certain reserved words called modifiers that specify the properties of the data, methods, and classes and how they can be used.

Examples of modifiers are public and static. Other modifiers are private, final, abstract, and protected. A public datum, method, or class can be accessed by other programs.A private datum or method cannot be accessed by other programs. Modifiers are discussed in Chapter 6, “Objects and Classes.”

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StatementsA statement represents an action or a sequence of actions.

The statement System.out.println("Welcome to Java!") is a statement to display the greeting "Welcome to Java!"

Every statement in Java ends with a semicolon (;).

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Blocks

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A pair of braces in a program forms a block that groups

components of a program.

public class Test { public static void main(String[] args) { System.out.println("Welcome to Java!"); } }

Class block

Method block


Classes

The class is the essential Java construct. A class is a template or blueprint for objects. To program in Java, you must understand classes and be able to write and use them.

For now, though, understand that a program is defined by using one or more classes.

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MethodsWhat is System.out.println?

It is a method: a collection of statements that performs a sequence of operations to display a message on the console.

It is used by invoking a statement with a string argument. The string argument is enclosed within parentheses. In this case, the argument is "Welcome to Java!" You can call the same println method with a different argument to print a different message.

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main MethodThe main method provides the control of program flow. The Java interpreter executes the application by invoking the main method. The main method looks like this:

public static void main(String[] args) { // Statements;}

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Displaying Text in a Message Dialog Box

you can use the showMessageDialog method in the JOptionPane class. JOptionPane is one of the many predefined classes in the Java system, which can be reused rather than “reinventing the wheel.”

WelcomeInMessageDialogBox

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Run IMPORTANT NOTE: To enable the buttons, you must store the entire slide file Link_Files files into a directory (e.g., e:\Link_Files_CSC210) .


The showMessageDialog Method JOptionPane.showMessageDialog(null, "Welcome to Java!", "Display Message", JOptionPane.INFORMATION_MESSAGE);

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Two Ways to Invoke the MethodThere are several ways to use the showMessageDialog method. For the time being, all you need to know are two ways to invoke it.One is to use a statement as shown in the example:

JOptionPane.showMessageDialog(null, x, y, JOptionPane.INFORMATION_MESSAGE);

where x is a string for the text to be displayed, and y is a string for the title of the message dialog box.The other is to use a statement like this:

JOptionPane.showMessageDialog(null, x);

where x is a string for the text to be displayed.32


PROGRAMMING EXERCISES(Displaying a pattern) Write a program that displays the following pattern:

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PROGRAMMING EXERCISES

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PROGRAMMING EXERCISES

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Write a program that asks the user to enter two numbers, then prints the sum, product, and difference of the two numbers.

l1-2:csc210 2014-2015 ©dr. basheer m. nasef lecture #1 by dr. basheer m. nasef

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